Shoutbox

Lightening rarely hits the ground in England though.(it's called fork lightening, btw) We mostly have sheet lightening(just flashes across the sky)

Both thunder and lightening carry electric currents of sorts, the car wouldn't need to be hit by lightening to be set off(infact it'd probably melt the tires right off if it was, as it uses the cars body as a way to earth it's self.) The sheer build up of electrical charge in the atmosphere could set it off(theoretically I guess, I imagine it'd have to be a pretty large charge for it to affect the cars simply from the atmosphere) which means both lightening and thunder.

Either way I doubt you wouldn't notice a storm big enough for that happen.